Arrangement for providing a compact battery with autonomous cooling

ABSTRACT

Arrangement for a compact battery and cooling system. The arrangement includes a plurality of elongate battery cells, each battery cell having a longitudinal axis and a hexagonal cross-sectional shape in a plane oriented substantially perpendicular to the longitudinal axis. The cells are parallelly oriented, each to the others, within a battery housing. Preferably, the cells are arranged in a honeycomb configuration with opposed faces of adjacent battery cells proximately located one to the other in face-to-face relationship. At least one substantially hexagonally shaped cooling channel is provided at an interior location within the plurality of battery cells.

RELATED APPLICATION(S)

This patent application claims priority to U.S. Provisional ApplicationNo. 60/245,090 filed Oct. 31, 2000 and entitled HYBRID ELECTRIC VEHICLE.Said application in its entirety is hereby expressly incorporated byreference into the present application.

DESCRIPTION

1. Industrial Applicability

The present invention finds applicability in the transportationindustries, and more specifically private and commercial vehicles. Ofparticular importance is the invention's incorporation into hybridelectric vehicles.

2. Background Art

Generally, a hybrid electric vehicle combines electric propulsion withtraditional internal combustion engine propulsion to achieve enhancedfuel economy and/or lower exhaust emissions. Electric propulsion hastypically been generated through the use of batteries and electricmotors. Such an electric propulsion system provides the desirablecharacteristics of high torque at low speeds, high efficiency, and theopportunity to regeneratively capture otherwise lost braking energy.Propulsion from an internal combustion engine provides high energydensity, and enjoys an existing infrastructure and lower costs due toeconomies of scale. By combining the two propulsive systems with aproper control strategy, the result is a reduction in the use of eachdevice in its less efficient range. Furthermore, and as shown in FIG. 1regarding a parallel hybrid configuration, the combination of adownsized engine with an electric propulsion system into a minimalhybrid electric vehicle results in a better utilization of the engine,which improves fuel consumption. Furthermore, the electric motor andbattery can compensate for reduction in the engine size.

In typical configurations, the combination of the two types ofpropulsion systems (internal combustion and electric) is usuallycharacterized as either series or parallel hybrid systems. In a pureseries hybrid propulsion system, only the electric motor(s) are indirect connection with the drive train and the engine is used togenerate electricity which is fed to the electric motor(s). Theadvantage of this type of system is that the engine can be controlledindependently of driving conditions and can therefore be consistentlyrun in its optimum efficiency and low emission ranges. A keydisadvantage to the series arrangement is the loss in energy experiencedbecause of the inefficiencies associated with full conversion of theengine output to electricity.

In a pure parallel hybrid propulsion system, both the engine and theelectric motor(s) are directly connected to the drive train and eitherone may independently drive the vehicle. Because there is a directmechanical connection between the engine and the drive train in aparallel hybrid propulsion system, less energy is lost throughconversion to electricity compared to a series hybrid propulsion system.The operating point for the engine, however, can not always be chosenwith full freedom.

The two hybrid propulsion systems can be combined into either aswitching hybrid propulsion system or a power-split hybrid propulsionsystem. A switching hybrid propulsion system typically includes anengine, a generator, a motor and a clutch. The engine is typicallyconnected to the generator. The generator is connected through a clutchto the drive train. The motor is connected to the drive train betweenthe clutch and the drive train. The clutch can be operated to allowseries or parallel hybrid propulsion.

A power-split hybrid system, as is exemplarily employed with respect tothe present invention, includes an engine, a generator and a motor. Theengine, output is “split” by a planetary gear set into a series pathfrom the engine to the generator and a parallel path from the enginedirectly to the power train. In a power-split hybrid system, the enginespeed can be controlled by varying the power split to the generator byway of the series path, while maintaining the mechanical connectionbetween the engine and drive train through the parallel path. The motoraugments the engine on the parallel path in a similar manner as atraction motor in a pure parallel hybrid propulsion system, and providesan opportunity to use energy directly through the series path, therebyreducing the losses associated with converting the electrical energyinto, and out of chemical energy at the battery.

In a typical power-split hybrid system, the generator is usuallyconnected to the sun gear of the planetary gear set. The engine isconnected to the planetary carrier and the output gears (usuallyincluding an output shaft and gears for interconnection with the motorand the wheel-powering, final drive train) are connected to the ringgear. In such a configuration, the power-split hybrid system cangenerally be operated in four different modes; one electric mode andthree hybrid modes.

In the electric mode, the power-split hybrid system propels the vehicleutilizing only stored electrical energy and the engine is turned off.The tractive torque is supplied from the motor, the generator, or acombination of both. This is the preferred mode when the desired poweris low enough that it can be produced more efficiently by the electricalsystem than by the engine and when the battery is sufficiently charged.This is also a preferred mode for reverse driving because the enginecannot provide reverse torque to the power train in this configuration.

In the parallel hybrid mode, the engine is operating and the generatoris locked. By doing this, a fixed relationship between the speed of theengine and the vehicle speed is established. The motor operates aseither a motor to provide tractive torque to supplement the engine'spower, or can be operated to produce electricity as a generator. This isa preferred mode whenever the required power demand requires engineoperation and the required driving power is approximately equal to anoptimized operating condition of the engine. This mode is especiallysuitable for cruising speeds exclusively maintainable by the smallinternal combustion engine fitted to the hybrid electric vehicle.

In a positive split hybrid mode, the engine is on and its power is splitbetween a direct mechanical path to the drive train and an electricalpath through the generator. The engine speed in this mode is typicallyhigher than the engine speed in the parallel mode, thus deriving higherengine power. The electrical energy produced by the generator can flowto the battery for storage or to the motor for immediate utilization. Inthe positive split mode, the motor can be operated as either a motor toprovide tractive torque to supplement the engine's power or to produceelectricity supplementally with the generator. This is the preferredmode whenever high engine power is required for tractive powering of thevehicle, such as when high magnitude acceleration is called for, as inpassing or uphill ascents. This is also a preferred mode when thebattery is charging.

In a negative split hybrid mode, the engine is in operation and thegenerator is being used as a motor against the engine to reduce itsspeed. Consequently, engine speed, and therefore engine power, are lowerthan in parallel mode. If needed, the motor can also be operated toprovide tractive torque to the drive train or to generate electricitytherefrom. This mode is typically never preferred due to increasedlosses at the generator and planetary gear system, but will be utilizedwhen engine power is required to be decreased below that which wouldotherwise be produced in parallel mode. This situation will typically bebrought about because the battery is in a well charged condition and/orthere is low tractive power demand. In this regard, whether operating asa generator or motor, the toque output of the generator is always of thesame sense (+/−); that is, having a torque that is always directionallyopposed to that of the engine. The sign of the speed of the generator,however, alternates between negative and positive values depending uponthe direction of rotation of its rotary shaft, which corresponds withgenerator vs. motor modes. Because power is dependent upon the sense ofthe speed (torque remains of the same sense), the power will beconsidered to be positive when the generator is acting as a generatorand negative when the generator is acting as a motor.

When desiring to slow the speed of the engine, the current beingsupplied to the generator is changed causing the speed of the generatorto slow. Through the planetary gear set, this in turn slows the engine.This effect is accomplished because the resistive force acting againstthe torque of the generator is less at the engine than at the driveshaft which is connected to the wheels and is being influenced by theentire mass of the vehicle. It should be appreciated that the change inspeed of the generator is not equal, but instead proportional to that ofthe engine because of gearing ratios involved within the connectiontherebetween.

In electric and hybrid electric vehicles, large capacity electricitystorage device(s), usually in the form of battery packs, are required.By conventional design, these batteries include a plurality ofcylindrical battery cells that are collectively utilized to obtainsufficient performance and range in the vehicle. Typically, batteriesare positioned within the vehicle in a compartment configured to protectagainst damage and to prevent the cells, and mostly their acidiccontents, from causing injury or damage, especially in the event of acrash. When stored in these typically confined compartment(s), heatbuildup generated from use and/or charging affects the endurance of thebatteries, and in some circumstances can destroy individual batterycells. Traditional cooling of the batteries and the battery compartmentrequires increasing the volume of the compartment for air cooling and/orrunning cooling hoses to external radiators.

Typically, to achieve a smooth engine start in a hybrid electric vehiclein which the engine is mechanically interconnected with the drivewheels, the start of engine fuel injection and ignition are made atrevolutionary speeds above any mechanical resonance speeds of the drivetrain. Additionally, at full take-off acceleration, any delay in theengine's production of power typically decreases engine performance.Still further, to achieve smooth driving characteristics and obtain lowfuel consumption, the engine torque and speed change rates must belimited. At full take-off, this usually results in an increased timeperiod for the engine to reach maximum power, and all of theseconditions deteriorate acceleration performance of the vehicle.

As can be appreciated, the engine is not always running during vehicleoperation. If the engine is stopped for a sufficiently long periodduring the operation of the vehicle, the exhaust system catalyst maycool down too much, and to such a degree that a temporary, butsignificant increase in exhaust emissions occur upon restart and untilthe catalyst once again warms to its effective temperature.

In another aspect, the battery state-of-charge (SOC) in a hybridelectric vehicle is typically controlled using SOC feedback control.When applying SOC feedback control, however, and when the vehicle isoperating in a low velocity region, the SOC feedback control tends togrow unstable as velocity increases. Instability also occurs when thevehicle is operating at high velocity and the velocity of the vehiclethen decreases. The same instability or weakness can still occur evenwhen using “feed-forward” type estimating of required tractive force;the same being a typical complement to SOC feedback control. This isparticularly true at low vehicle velocities with velocity increases andat high vehicle velocities with velocity decreases. Even when properlydesigned, the SOC feedback control can also be weak at full take-off.

In a typical power-split hybrid electric propulsion arrangement, thecontrol strategy advantageously involves operating the engine alongoptimum efficiency torque vs. speed curves. A trade-off exists betweentraction force performance and fuel economy which, for optimization,typically requires selection of a particular gear ratio between theengine and the wheels that causes the engine to deliver more power thanis needed for vehicle propulsion. This generally occurs at cruising inparallel mode, or near constant vehicle velocity conditions. Operationunder these conditions can, sometimes, cause the battery and chargingsystem to reject energy being presented thereto from the engine. Thisproblem is generally solved by decreasing or limiting the engine outputpower by entering negative split mode which entails using the generatoras a motor to control the engine to a decreased speed. Such controlallows the engine to follow an optimum curve at reduced engine outputpower.

Use of the generator as a motor gives rise to a power circulation in thepower-train which leads to undesirable energy losses at the generator,motor, inverters and/or planetary gear set. These energy losses may bemanifest as heat generation which indicates that most efficient use isnot being made of the installed drive train.

In a power-split hybrid propulsion system having planetary gear set(s)and utilizing a generator lock-up device, a harshness in ride occurswhen the generator lock-up device is engaged or released. This is dueprimarily to the difference in how engine torque is estimated when thevehicle is in different operating modes. Typically, when the generatoris locked up, engine torque is estimated from the combustion controlprocess of the engine. When the generator is free, as in split mode,however, engine torque is estimated from the generator torque controlprocess. The difference in values of these two estimating techniquesgives rise to what usually amounts to a variation in operating torquebetween the engine and generator when the lock-up device is engaged ordisengaged, thereby creating harshness in the vehicle's operation,usually manifest as abrupt changes or jerkiness in the vehicle's ride.

As earlier indicated, the generator is typically used to control theengine in power-split hybrid mode. This is usually accomplished byemploying a generator having maximum torque capabilities substantiallygreater than the engine's maximum torque that is transmittable to theplanetary gear system. Failure to have such a control margin can resultin generator over-speed and possible damage to the propulsion system.Such a control margin means, however, that the engine and generator arenot fully exploited at full capacity acceleration.

Several deficiencies associated with the use of known hybrid electricvehicle designs and methods of operating the same have been describedhereinabove. Several inventive arrangements and methods for operatinghybrid electric vehicles are described hereinbelow that minimize, orremedy these deficient aspects of known designs, and/or providebenefits, in and of themselves, to the user. These new, improved andotherwise potentiated solutions are described in greater detailhereinbelow with respect to several alternative embodiments of thepresent invention.

DISCLOSURE OF THE INVENTION

In a first aspect, an arrangement for a compact battery and coolingsystem therefore is disclosed. The arrangement includes a plurality ofelongate battery cells, each battery cell having a longitudinal axis anda hexagonal cross-sectional shape in a plane oriented substantiallyperpendicular to the longitudinal axis. The cells are parallellyoriented, each to the others, within a battery housing. Preferably, thecells are arranged in a honeycomb configuration with opposed faces ofadjacent battery cells proximately located one to the other inface-to-face relationship. At least one substantially hexagonally shapedcooling channel is provided at an interior location within the pluralityof battery cells.

In a second aspect, a method for potentiating an engine's powercontribution to a hybrid electric vehicle's performance in a take-offoperating condition is disclosed. Normally, fuel injection to, andignition at the engine are only commenced when the engine is operatingat a speed exceeding the resonance speed of the drive train to reduceengine start harshness; such resonance speeds of the drive train beingdictated, at least in part, by transmission backlash, softness and thelike. During high driver acceleration demands, however, ignition and theinjection of fuel is desirably started as early as possible topotentiate output power and acceleration.

In a third aspect, a method for maintaining a catalyst of an emissionssystem in a hybrid electric vehicle in an operative condition isdisclosed. The method includes sensing that an engine of a hybridelectric vehicle has stopped operating. A time period is predicted afterwhich a catalyst of an emissions system associated with the engine willcool to a light-off temperature below which the catalyst becomesineffective. The predicting step is based on known qualities of thecatalyst and ambient conditions in which the vehicle is being operated.The engine is restarted when the predicted time period has expiredthereby maintaining the catalyst at temperatures in excess of thelight-off temperature.

In a fourth aspect, a method for minimizing driver perceptible drivetrain disturbances during take-off in a hybrid electric vehicle whenmaximized power is often desired is disclosed. The method includessensing an actual state-of-charge (SOC) value of a battery in a hybridelectric vehicle and a traveling velocity of the vehicle during take-offoperation. The sensed actual SOC value is compared with a SOC referencevalue and computing a delta SOC value as a difference therebetween. Avelocity-based SOC calibration factor is looked up that corresponds tothe traveling velocity of the vehicle. A combination is utilized of thedelta SOC value and the SOC calibration factor as a SOC feedback enginespeed control instruction to an engine controller of the hybrid electricvehicle. A driver's desired vehicular acceleration is sensed based onaccelerator position. Maximum possible engine power generatable at thesensed vehicle speed is determined, as is a required power value fromthe power train of the vehicle to meet the driver's desired vehicularacceleration. The maximum possible engine power generatable at thesensed vehicle speed is compared with the required power value andcomputing a delta power train requirement value as a differencetherebetween. A velocity-based and accelerator position-based powercalibration factor is looked-up that corresponds to the travelingvelocity of the vehicle and the accelerator position. A combination ofthe delta power train requirement value and the power calibration factoris utilized as a power requirement feed-forward engine speed controlinstruction to an engine controller of the hybrid electric vehicle.

In a fifth aspect, a method for optimizing the operational efficiency ofa hybrid electric vehicle is disclosed. The method comprises operatingan engine of a hybrid electric vehicle preferentially on an optimizedpower curve of the engine for maximizing the efficiency of the engineand sensing a state-of-charge (SOC) condition of a battery of the hybridelectric vehicle being at a preferential value indicative of noadditional charging being desired. The running torque of the engine isreduced below the optimized torque curve to a point that the powerproduced by the engine is substantially equal to the power demanded fordriving the hybrid electric vehicle.

In a sixth aspect, a method for calibrating and synchronizing sensedoperating torques of an engine and a generator in a planetary gear basedhybrid electric vehicle is disclosed. The method includes providing asensor that detects the operational torque of an engine of a hybridelectric vehicle at the engine's interface with a planetary gear systemof the hybrid electric vehicle. A sensor is provided that detects theoperational torque of a generator of a hybrid electric vehicle at themotor's interface with the planetary gear system of the hybrid electricvehicle. The planetary gear system of the hybrid electric vehicle isoperated in a split mode so that the generator is directly linked to theengine and a reading of the sensor that detects the operational torqueof the generator may be used to compute the operating torque of theengine. Paired values of sensed operational torques of the engine andthe generator at like times are recorded. Each pair of recorded valuesare arithmetically processed and a calibrating value is computedtherebetween. The sensing and recording of paired values is repeated atthe same sensed generator and engine speeds and torques thereby enablingthe calculation of computed average calibrating values at each of theparticular sensed generator speeds suitable for subsequent utilizationin computing corresponding engine torques in the future. The engine andthe generator are controlled utilizing the average calibrating value atfuture times of transition between power-split mode and parallel mode ofthe planetary gear system so that the engine is substantiallysynchronized with the generator at the time of direct linkage across theplanetary gear arrangement thereby avoiding driver detectibleirregularities in the performance of the power train of the hybridelectric vehicle.

In a seventh aspect, a method for potentiating the utilizable torqueoutput capacity of a hybrid electric vehicle is disclosed. The methodincludes controlling operation of an engine of a hybrid electric vehicleusing a generator, the engine and generator being interconnected througha planetary gear system, the generator having approximately equal torqueoutput capacity as the engine based on connective gear ratio selection.An engine controller is utilized for managing the engine's operationthereby permitting the engine to be operated at a torque output levelsubstantially equal to the maximum torque output of the generatorwithout a significant margin of excess control capacity of the generatorover the engine. An overpower condition is detected in which the torqueoutput of the engine is surpassing the maximum torque output of thegenerator. The engine is controlled to a torque output that is less thanthe maximum torque output of the generator.

The general beneficial effects described above apply generally to theexemplary descriptions and characterizations of the devices, mechanismsand methods disclosed herein. The specific structures and steps throughwhich these benefits are delivered will be described in detailhereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in greater detail byway of examples and with reference to the attached drawings, in which:

FIG. 1 is a graphical comparison of torque generated by a parallelhybrid and systems that have either an engine or motor.

FIG. 2 is a perspective of a hybrid electric vehicle showing exemplarilysystem component locations on the vehicle.

FIG. 3 is a schematic depicting the architecture of a power-split hybridelectric vehicle.

FIG. 4 is a cross-sectional schematic representation of a planetary gearset.

FIG. 5 is a simplified schematic view of a one-way clutch shown in FIG.2.

FIG. 6 is a schematic depicting control relationships between thevarious systems of a hybrid electric vehicle as coordinated utilizingthe CAN.

FIG. 7 is a functional schematic depicting the processes, tasks andcontrols of the various systems of the exemplary hybrid electricvehicle.

FIG. 8a is a schematic horizontal cross-sectional view of a battery fora hybrid electric vehicle according to one aspect of the presentinvention(s).

FIG. 8b is a schematic horizontal cross-sectional view of a traditionalbattery having cylindrically-shaped cells.

FIG. 8c is a schematic vertical cross-sectional view of a batterycooling system as depicted in FIG. 8a.

FIGS. 9 and 10 schematically illustrate a method for minimizing driverperceptible drive train disturbances during take-off in a hybridelectric vehicle.

FIGS. 11 through 15 schematically illustrate a method for potentiatingthe utilizable torque output of a particularly sized engine in a hybridelectric vehicle.

MODE(S) FOR CARRYING OUT THE INVENTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention(s) that may be embodied in variousand alternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as abasis for the claims and as a representative basis for teaching oneskilled in the art to variously employ the present invention.

As depicted in FIGS. 1 and 2, a hybrid electric transporting vehicle 10has a power train system (having components generally designated withreference numbers from the 500's series) included therein for providingpropulsion, as well as serving supplemental functions which aredescribed in greater detail herein. Predominantly, the power trainsystem is positioned in an engine room 11 located near a passengercompartment 12 of the vehicle 10. A battery compartment or housing 14,also positioned near the passenger compartment 12 holds one or morebatteries 410. As will be appreciated by those skilled:in the art, thepositioning of both the engine room 11 and battery housing 14 is notlimited to the locations set forth in FIG. 2. For example, either may bepositioned in front of, or behind the passenger compartment 12.

As depicted in FIG. 2, the overall systems architecture of the electrichybrid vehicle 10 comprises an engine system 510, including an internalcombustion engine 511 (petrol, diesel or the like), that is mechanicallyconnected by an output shaft system 520 to a transaxle system 530. Thetransaxle system 530 is further connected to a drive shaft system 540utilized to rotate one or more drive wheels 20 that propel the hybridelectric transporting vehicle 10. In a preferred embodiment, thecombustion engine 511 is controlled by an engine control module (ECM) orunit 220 which is capable of adjusting, among possible parameters,airflow to, fuel flow to and/or ignition at the engine 511. The engine511 is mechanically connected via an output shaft 522 to the transaxlesystem 530. A planetary gear set 535 establishes interconnection betweenthe engine 511 (via the output shaft 522), a generator 532, and thedrive shaft system 540 (via the transaxle system 530). A motor 531 isalso coupled to the drive shaft system 540, also possibly via thetransaxle system 530.

In one embodiment, and which is illustrated in at least FIGS. 3 and 5, aone way clutch 521 is engageable with the output shaft 522, which inturn is connect to the engine 511 and to the planetary gear set 535. Thefunction of the one-way clutch 521 is to limit the engine to being onlya power/torque input to the planetary gear set 535, and with only onedirection of rotation. Consequently, the one-way clutch 521 preventspower or torque from being transmitted from the planetary gear set 535back to the engine 511.

In another aspect, and as shown in FIG. 4, the planetary gear set 535comprises a plurality of concentrically positioned planet gears 539mechanically engaged between a perimeter region of a centrally locatedsun gear 538 and an interior surface of a ring gear 537. The individualgears that make up the plurality or set of planet gears 539 are fixed inpositions relative to each other by a planetary carrier 536.

The generator 532 is mechanically connected to the sun gear 538 and isconfigured to convey rotational power and torque to and from theplanetary gear set 535. In a preferred embodiment, the generator 532 iscapable of being locked to prevent rotation of the sun gear 538 by agenerator brake or lock-up device 533. As further contemplated by thepresent invention, the motor 531 is mechanically connected to the ringgear 537 and is configured to convey rotational power and torque to andfrom the planetary gear set 535. In a preferred embodiment, and asschematically shown in FIG. 3, the drive shaft system 540 is engagablewith the motor 531 and effectively terminates at the drive wheel 20, viawhat can be a conventionally configured transmission/differentialarrangement 542.

Based on the above disclosed system architecture, implementation of anenergy management strategy, which is a focus of the hybrid electricvehicle 10, starts at a high level within a vehicle control unit orvehicle systems controller (VCU) 100 as schematically shown in FIGS. 6and 7. The vehicle systems controller 100 is programmed with controlstrategies for the drive train system and battery system, as well asothers. The vehicle systems controller 100 is responsible forinterpreting driver inputs, coordinating the component controllers, anddetermining vehicle system operating states. The VCU 100 also generatescommands to appropriate component sub-systems based on defined vehiclesystems controller 100 functions, and sends those commands to thecomponent controllers that, based thereon, take appropriate actions. Thevehicle systems controller 100 also acts as a reference signal generatorfor the sub-system controllers. The vehicle systems controller 100 maytake the form of a single, integrated microprocessor, or comprisemultiple microprocessors that are suitably interconnected andcoordinated.

A primary function of the vehicle systems controller 100 is to carry outvehicle mode processes and tasks (also known as the sequential controlprocess), as well as make torque determinations, set reference valuesand perform energy management processes. Certain systems of the vehicle10 are managed or monitored by a vehicle management (VM) unit orcontroller 105 which carries out sequential control processes, includingascertaining the position of the vehicle key and gear selectorpositioning, among others. It is at this level that certain inputs fromthe driver and conditions of the vehicle are synthesized for utilizationas command inputs for sub-system controllers.

At the lower level of the VCU 100, three sub-component controllers areillustrated in FIG. 7. The first is a high voltage DC controller (HVDC)115; the second is a battery management unit or controller 110 (bbb);and the third is a drive train controller 120 (DTC). As indicated above,certain inputs and processes are taken from the driver and the vehicle'ssystems at the vehicle management unit 105. Conversely, certain outputsrelevant to the driver will be transmitted and displayed at thedashboard display unit 107 from the VCU 100 or the VM 105.

The HVDC 115 is responsible for coordinating operation of the highvoltage components. The positioning of this controller is schematicallyshown in FIG. 6. The HVDC contains contactors or breakers which arenormally positioned to an open configuration that prevents electricityfrom flowing thereacross. But when called on to take action and engagethe battery 410, for instance when starting of the engine 511 isrequired, these contractors (usually a pair) close completing anappropriate connective circuit.

As shown in FIG. 6, the HVDC serves as a shield or buffer between thehigh voltage battery 410, and the inverters 534, as well as otherauxiliary loads run off of the electric power of the battery 410. Anexample of such a high voltage auxiliary load may include anelectrically run air-conditioning compressor system. In order to act assuch a buffer, the high voltage output from the battery 410 must berelatively slowly “brought-up” to operating levels at the inverter 534and/or auxiliary loads. In order to accept this “run-up” of the voltage,relatively small capacity contactors are initially closed that causevoltage from the battery to pass to a capacitor in either the inverter534 or the appropriate auxiliary load, across a resistive circuit (acircuit containing buffering resistors). Once an appropriate pre-chargeis built-up in the capacitor, primary contractors are then closed whichcomplete the high voltage circuit between the batteries 410 and thecapacitor contained within the receiving component which may beexemplified by the DC to AC inverter(s) 534, or an auxiliary load suchas an electric air-conditioning system as indicated hereinabove. In thismanner, a potentially damaging high voltage is prevented from beingintroduced too quickly to the receiving components.

The HVDC 115 also carries out certain diagnostic functions regarding thecomponents of the HVDC 115, such as the contactors within the HVDC 115itself, and also possibly the several systems interconnected through theHVDC, such as the battery 410, the inverters 534, or an electricallydriven air-conditioning compressor which has not been illustrated in theFigures. Among other parameters, these diagnostics may be performedbased on measurements of voltage and/or current.

The HVDC 115 also provides interconnection between an exterior chargerconnection (see ext. charger in FIG. 6), thereby allowing the battery410 to be “plugged-in” for charging from an external power source.

The battery management controller (BMU) 110 handles control tasksrelative to the battery system 410. Among other characteristics, the BMU110 can estimate and measure state-of-charge (SOC) levels, and voltageand current parameters. It can also sense/determine and maintain maximumand minimum voltage and current levels with respect to the battery 410.Based on these determinations or sensed quantities/qualities, the VM 105, via such control modules as the DTC 120, can direct certain operationsfor affecting changes in the SOC of the battery 410. Othercharacteristics which may be monitored include operating temperature(s)of the battery 410, and voltages at the individual battery cells 412.Similarly, pressure within the cells 412 can also be monitored. Failuresmay be detected and reported, at least back to the VCU; but there isalso the possibility of the information being passed to the operator viathe dashboard display unit 107.

The DTC 120 makes the mode selection under which the several poweringcomponents will cooperate. That includes choices between parallel andsplit modes, as well as positive and negative split modes. Theoperational points for the several components of the drive train arealso specified by the DTC 120. Still further, reference values areprovided by the DTC 120 for the several sub-systems, including thetransaxle management control modules or unit (TMU) 230 and the enginecontrol module or unit (ECM) 220. From among the possible settingsestablished by the DTC 120, battery charging/discharging mode is apossibility, as well as specifying whether the generator 532 and/ormotor 531 should be used in their powering capacity as a motor, or theirgenerating capacity as a generator. Torque references for the generatorand motor are also issued from the TMU 230.

As a sub-component under the TMU 230, the transaxle control unit TCU 232handles the transaxle 530 with respect to torque compensation whenstarting and stopping the engine 511. The TCU 232 uses and controls twoslave processors characterized as a generator control unit GCU 236 and amotor control unit MCU 234. The GCU 236 handles the current and torquecontrol of the generator 532; typically, via the inverter 534. The GCU236 receives its torque and speed reference information from the TCU 232as its immediate controller. The TCU 232 receives a total torquereference for the transaxle 530 and the speed reference value for theengine 511, together with mode reference information regardingcooperation between the engine 511 and generator 532; such as, whetherparallel-, positive-split, or negative-split mode configurations will beassumed. The TCU 232 generates the torque reference parameters for thegenerator 532 and motor 531, each of which are implemented under thecontrol of the GCU 236 and MCU 234, respectively. The specified torquesettings are accomplished by controlling the current provided,to therespective generator/motor controllers 236,234.

Based on a map of optimal engine torque vs. speed curves, engine speedand torque are selected by the DTC 120 so that the engine system 510 candeliver the desired engine power and simultaneously lie on one of theengine's optimized efficient curves. If the DTC 120 determines that thespeed of the engine 511 is too low for efficient operation, then theengine 511 is turned (or left) off by the engine control unit 220. Ifthe power train control module 120 determines that the speed of theengine 51 is too high to be controlled by the generator 532 (based onSOC and generator limitations), the engine 511 is set to a slowedoperational speed by the ECM 220.

Once the speed, torque and power of the engine 511 are determined by thevehicle systems controller 100, particularly at the DTC 120 of thecontroller 100, then the DTC 120 further determines the required speedand torque of the generator 532 to control the engine 511. The DTC 120,using this information, then determines the required speed and torque ofthe motor 531 to meet the difference, if any, between driver power(torque) demand and the engine power (torque).

Torque determination and monitoring is also carried out at the VCU 100.This function further ensures that torque delivered to the drivewheel(s) 20 is substantially equal to the torque (acceleration) demandedby the driver. The VCU 100 also monitors and controls the torque fromthe engine 511 and transaxle system 530 by comparing a sensed torqueagainst the torque demanded by the driver. Torque management by the VCU100 interprets driver inputs and speed control demands to determineregenerative brake torque and desired output shaft torque.

From the VCU 100, commands and references are distributed over acontroller area network (CAN) 300 to component controllers generallyreferenced herein utilizing reference numbers in the 200's series. Asindicated above, these controllers include the ECM 220 and the TMU 230that together control the power train system to achieve efficient energymanagement, partition torque, determine engine 511 operating point(s),and decide on, and coordinate engine 511 start/stops. Commands andreferences from the VCU 100 to a series regenerative brake controllerdetermine regeneration torque limitations, desired regenerative torqueand zero vehicle speed control.

Finally, if and/or when individual system components are renderedinoperative, such as the motor 531 becomes disabled, the VCU 100 isconfigured to provide limited operating control over the power trainsystem to allow the hybrid engine vehicle 10 to “limp” home.

As shown in FIG. 8a, a compact battery system 400 is made up of a numberof elongate battery cells 412, each cell 412 having a longitudinal axisand a hexagonal cross-section shape in a plane oriented substantiallyperpendicular to the longitudinal axis. Each cell 412 is parallellyoriented to each other within a battery housing 14. As shown in FIG. 8a,the plurality of cells 412 are arranged in a honeycomb configurationwith opposed faces of adjacent cells 412 proximately located one to theother in face-to-face relationship. One or more hexagonally shapedcooling channels 442 are located at an interior location(s) amongst theplurality of battery cells 412. As appreciated by those skilled in theart, a significant amount of volume is unused and wasted in batterycompartments configured to hold traditional cylindrical battery cells asis exemplarily depicted in FIG. 8b. Furthermore, the traditional coolingsystem often requires the use of a system of fluid filled pipes to coola fraction of the cylindrically shaped battery cells curved exteriorsurface. In contrast, the battery cooling system 440 for the hexagonalbattery cells 412, as depicted in FIG. 8a, presents a greater surfacearea for heat exchange to take place.

In another aspect of the system 440, and as is shown in FIG. 8c, athermally radiative cap 443 is in fluid communication with one or moreof the cooling channels 442 which is filled with a cooling fluid 445that circulates between the cap 443 and the channels 442 to cool thebattery cells 412. The cooling fluid 445 may consist of water maintainedunder a vacuum so that it boils at approximately 40° centigrade.Circulation of the fluid, as well as transformation between the gaseousand liquid states, occurs because of the temperature differentialbetween the warmer lower area among the battery cells 412 and the coolerupper area with the cap 443. Exemplarily, this temperature ofvaporization or boiling advantageously falls between these warmer andcooler temperatures.

An air circulation system cools the battery arrangement by drawing airthrough an air inlet exposed to the passenger compartment 12 and directsthe air along a circulation path that crosses the radiative cap 443. Thetemperature of the air drawn from the passenger compartment 12 isnormally in a range suited for passenger comfort, a temperature normallywell below 40° centigrade. The intake may also pull air from outside thevehicle if ambient conditions are favorable. Air source selection may beeasily accomplished using a flap-style valve common in other air ductenvironments.

After traversing the circulation path, the cooling air is mostpreferably discharged away from the passenger compartment 12 to avoidcirculation and the introduction of heat and potentially airbornecontaminants into the passenger compartment 12 that may have been pickedup from the battery system 400. The risk of this occurrence, however, isreduced significantly through this battery's 410 configuration in whichthe circulated air passes over the closed system of the battery and itshousing, and not through or near the more hazardous chemical cells 412.

To further promote cooling, the radiative cap 443 may be configured witha plurality of fin-type members 444 that extend from an exteriorlyexposed surface thereof for enhancing thermal discharge of heat from thecap 443 to air circulated across the fins 444.

In another aspect, the disclosed invention(s) include a method forpotentiating an engine's 511 power contribution to a hybrid electricvehicle's 10 performance in a take-off operating condition. Normally,fuel injection to, and ignition at the engine 511 are only commencedwhen the engine 511 is operating at a speed exceeding the resonancespeed of the drive train to reduce engine start harshness; suchresonance speeds of the drive train being dictated, at least in part, bytransmission backlash, softness and the like. During high driveracceleration demands, however, ignition and the injection of fuel isdesirably started as early as possible to potentiate output power andacceleration. The present method amends this typical operation andincludes initiating take-off acceleration of the vehicle 10 exclusivelyusing the motor 531, predicting the future demand for an engine's 511power contribution to the vehicle's 10 immediate future power demandduring the take-off acceleration, and starting the engine 511 at thetime that the determination is made of future demand for the engine's511 power contribution during the take-off acceleration. This fulltake-off control method or process further includes making theprediction of future demand at the initiation of take-off accelerationand/or increasing the speed of engine 511 operation as rapidly aspredetermined operating efficiency parameters permit. The full take-offcontrol method which increases the speed of engine 511 operation asrapidly as predetermined operating efficiency parameters permit may alsoinclude a step of allowing the increase in speed of engine operation toprogress to a predetermined peak efficiency rate and diverting excesspower from the engine 511 to the generator 532 that generateselectricity with the diverted power. This full take-off control methodwhich increases the speed of the engine 511 operation as rapidly aspredetermined operating efficiency parameters permit, may also include astep of allowing the increase- in speed of engine 511 operation toprogress to a predetermined peak efficiency rate which enables exclusiveutilization of the engine 511 to meet the entirety of the vehicle's 10future power demand and reducing the motor's 531 contribution to thepower supplied to the vehicle 10 so that no excess power above demand issupplied by the engine 511.

In still a further aspect, the present invention provides a process ormethod for maintaining a catalyst 702 of an emissions system 700 in ahybrid electric propulsive system in an operative state. The methodcalls for sensing that the engine 511 has stopped operating. A timeperiod is then predicted after which the catalyst 702 will cool downbelow a temperature (also known as a light-off temperature) at which thecatalyst becomes ineffective. Pursuant thereto, the engine 511 isrestarted when the time period has expired or lapsed, therebymaintaining the catalyst 702 at temperatures in excess of the light-offtemperature, regardless of whether power is need from the engine 511 atthat time. Predicting the time period after which the catalyst 702 willcool down takes into consideration known qualities of the catalyst 702and ambient conditions in which the hybrid electric vehicle 10 is beingoperated. Such known qualities of the catalyst 702 include, but are notlimited to, heating and cooling characteristics of the catalyst 702,life expectancy of the catalyst 702, and age of the catalyst 702.Relevant ambient conditions in which the vehicle 10 is being operatedinclude, but are not limited to, weather and environmental conditionssuch as temperature, humidity and contaminant loads, as well as trafficconditions and road conditions. As an example, if driving is occurringin hilly terrain, this can be sensed as a cyclical demand for enginepower for recurring uphill climbs. If this is quantified, it may beconsidered in the control parameter as a predictable occurrence.Additionally, the system may take into account sensed or “learned”driver habits or performance for predicting purposes which can includethe a particular driver's demand for power is cyclical or otherwisepatterned. This may be typified by some drivers' bad habit of repeatedlyaccelerating to a speed, and then subsequently slowing therefrom. Whenthe decrease in speed is realized by the driver, rapid acceleration isthen demanded for again setting the desired travel speed. If the controlsystem “learns” such a pattern, it may be utilized in the predicting orcalculating process for maximum elapse time before the catalystexcessively cools.

This method for maintaining the exhaust catalyst 702 in an operativecondition may also include sensing the catalyst's 702 temperature andinitiating operation or stopping of the engine 511 when a predeterminedtemperature is detected. Because of the hybrid's 10 characteristics, thecatalyst maintenance process may further include running the engine 511at idle speed when temperature elevation is required and charging thebatteries 410 with the power produced from the idling engine 511. Analternative aspect to this process calls for heating the catalyst 702 toa predetermined temperature differential above the light-off temperatureand then stopping operation of the engine 511 when the predeterminedtemperature differential is achieved. Engine operation is stopped whenthe predetermined temperature differential is detected by a temperaturesensor 704 monitoring the temperature of the catalyst 702 or ispredicted by a catalyst temperature model.

A method for minimizing driver perceptible drive train disturbancesduring take-off driving in a hybrid electric vehicle 10 when maximizedpower is often desired is also described herein. The concepts of thismethod are illustrated in FIGS. 9 and 10. The method includes sensing anactual state-of-charge (SOC) value of the battery 410 in a hybridelectric vehicle 10 and a traveling velocity of the vehicle 10 duringtake-off operation. The sensed actual SOC value is compared with a SOCreference value and a delta SOC value is computed as a differencetherebetween. A velocity-based SOC calibration factor corresponding tothe traveling velocity of the vehicle 10 is obtained from a look-uptable maintained in the control system. A combination of the delta SOCvalue and the SOC calibration factor are utilized as a SOC feedbackengine speed control instruction to the engine control unit (ECM) 220 ofthe hybrid electric vehicle 10. A driver's desired vehicularacceleration based on accelerator position is also sensed. A maximumpossible engine power generatable at the sensed vehicle speed isdetermined, as is a required power value from the power train of thevehicle to meet the driver's desired vehicular acceleration. The maximumpossible engine power generatable at the sensed vehicle speed iscompared with the required power value and a delta power trainrequirement value is computed as a difference therebetween. Avelocity-based and accelerator position-based power calibration factorcorresponding to the traveling velocity of the vehicle and theaccelerator position is determined from a second look-up table. Acombination of the delta power train requirement value and the powercalibration factor is utilized as a power requirement feed-forwardengine speed control instruction to the engine controller 220 of thehybrid electric vehicle 10.

The combination of the delta SOC value and the SOC calibration factor isby multiplication, as is the combination of the delta power trainrequirement value and the power calibration factor is by multiplication.

In a separate or enhancing aspect of the method outlined immediatelyabove, a take-off vehicle operating condition is detected in whichmaximized power is likely to be demanded from the drive train of thehybrid electric vehicle 10. A sensed SOC discharge condition during thetake-off operation due to motor utilization of battery power isprevented from triggering a battery charging condition which wouldreduce engine torque available to power the drive train of the vehicle10. Alternatively, and/or additionally, immediate acceleration of theengine's 511 operation beyond an optimized operational speed inanticipation of an actual maximized power demand is initiated. Stillfurther, a command may be issued from a generator controller (GCU) 236,responsive to a sensed SOC discharge condition, instructing immediateacceleration of the engine's 511 operation beyond an optimizedoperational speed thereby minimizing discharge of the battery 410 orcommencing recharge of the battery 410.

A preferred SOC reference value, of exemplarily , but not necessarily,fifty percent of battery 410 total charge capacity, is utilized in atleast one embodiment of the invention; on others, a more lenient rangeof forty to sixty percent of battery total charge capacity may beobserved.

In another aspect, the invention takes the form of a method foroptimizing the operational efficiency of a hybrid electric vehicle 10.The method includes operating an engine 511 of a hybrid electric vehicle10 preferentially on an optimized power curve of the engine 511 formaximizing the efficiency of the engine 511. A state-of-charge (SOC)condition of a battery 410 of the hybrid electric vehicle 10 is sensedand constitutes a preferential value indicative of no additionalcharging being desired. At cruising, however, the engine power output inparallel mode is too large along the engine's 511 optimized power curve,particularly in view of gear ratios set by acceleration requirements.Instead of using negative-split mode and suffering the inherent lossesof that configuration, the running torque of the engine 511 in parallelmode is reduced to a level below the optimized torque curve to a pointthat the power produced by the engine 511 is substantially equal to thepower demanded for driving the hybrid electric vehicle

The reduction in engine torque is affected by adjusting airflow to, fuelflow to and/or ignition parameters of the engine 511.

The drive train of the hybrid electric vehicle 10 is thus reconfiguredfrom a negative power-split mode in which engine power is split througha planetary gear arrangement 535 between the drive wheels 20 and thegenerator 532 to a parallel mode in which the generator 532 is lockedand all engine power is output to the drive wheels 20 of the hybridelectric vehicle 10 through the planetary gear arrangement 535. Thisparallel mode, but with reduced and non-optimized engine operation, isused when efficiency is higher in this mode than if using negativesplit,mode for the same torque output.

As a goal, the time spent in negative power-split mode is minimized andtime spent in parallel mode is maximized. Utilization of the generatorto motor the engine 511 to a slowed operational speed is avoided usingthis process thereby avoiding sequential charge and discharge cyclesthrough the drive train components of the hybrid vehicle. Energy lossesin the power train of the hybrid electric vehicle 10 are thereforereduced by avoiding charge and discharge of the hybrid electricvehicle's battery system 400. Cooling requirements for the hybridelectric vehicle's battery 410 are also reduced since battery losses aredecreased.

In yet another aspect, the present invention takes the form of a methodfor calibrating and synchronizing sensed operating torques of the engine511 and the generator 532 in a planetary gear based hybrid electricvehicle 10. The method includes providing a sensor that detects theoperational torque of the engine 511 at the engine's interface with theplanetary gear system 535 (power-split hybrid drive train) of the hybridelectric vehicle 10. A sensor is provided that detects the operationaltorque of the generator 532 at its interface with the planetary gearsystem 535 of the hybrid electric vehicle 10. The planetary gear system535 of the hybrid electric vehicle 10 is operated in the split mode sothat the generator 532 is directly linked to the engine 511 and areading of the sensor that detects the operational torque of thegenerator 532 may also be used to compute the operating torque of theengine 511. Paired values of sensed operational speeds of the engine 511and the generator 532 at like times are recorded. Each pair of recordedvalues is arithmetically processed and a calibrating value therebetweenis computed. The sensing and recording of paired values at the samesensed generator and engine operation points is repeated therebyenabling the calculation of computed average calibrating values at eachof the particular sensed generator and engine speeds and torquessuitable for subsequent utilization in computing correlating enginetorques in the future. The engine 511 and the generator 532 arecontrolled utilizing the average calibrating value at future times oftransition between power-split mode and parallel mode of the planetarygear system 535 so that the engine torque is substantially matched withthe generator torque at the time of direct linkage across the planetarygear arrangement (i.e., when releasing generator lock-up), therebyavoiding driver detectible irregularities or harshness in theperformance of the power train of the hybrid electric vehicle 10.

The predictability of the relationship between the engine 511 andgenerator 532 in the parallel mode is based on gear ratios that remainsubstantially unchanging.

Contemporaneously measured values of complementary operating parametersof the hybrid electric vehicle 10 may also be recorded for each pair ofrecorded values of sensed operational torques of the engine 511 and thegenerator 532 to be used supplementally in the torque matching process.

To maintain trueness, the average calibration value is permitted to bevaried by a limited maximum value with respect to time so that anomalousdisturbances do not significantly impact the computed averagecalibration value. The updating of the computed average calibrationvalue for a particular generator sensed speed is ongoing, and continuousthereby continually improving the quality of the average calibrationvalue for that particular generator sensed speed.

The irregularities to be avoided are manifest as jerking motions inducedin the hybrid electric vehicle 10 by the planetary gear system 535.Customization of the computed average calibration value to an individualvehicle is enabled via the invention in the presently disclosedembodiment since histories are taken, maintained, and considered in thematching process.

Referring to FIGS. 11-15, yet another aspect of the present invention isdisclosed. This aspect takes the form of a method for potentiating theutilizable torque output capacity of a hybrid electric vehicle 10. Themethod includes controlling operation of the engine 511 of the hybridelectric vehicle 10 using the generator 532, the engine 511 andgenerator 532 being interconnected through the planetary gear system535. The generator 532 has approximately equal torque output capacity asthe engine 511 when connecting gear ratios are considered. An enginecontroller 220 is utilized for managing the engine's 511 operationthereby permitting the engine 511 to be operated at a torque outputlevel substantially equal to the maximum torque output of the generator532 without a significant margin of excess control capacity of thegenerator 532 over the engine 511. An overpower condition is detected inwhich the torque output of the engine 511 is surpassing the maximumtorque output of the generator 532. Responsively, the engine 511 iscontrolled to a torque output that is less than the maximum torqueoutput of the generator 532.

The method continues by rechecking for a continuation of the engineoverpower condition and shutting the engine 511 down if the controlactions are not sufficient and a continuing overpower condition isdetected. In this manner, generator and engine over-speed is avoided.

By this process, total utilizable capacity of the hybrid electricvehicle's power plant is optimized by enabling running the engine 511 atsubstantially maximum capacity where greatest torque is producedtherefrom.

Available take-off torque in the hybrid electric vehicle 10 is optimizedby running the engine 511 at substantially maximum torque capacitytogether with a commensurately sized, but not oversized, generator 532with respect to relative torque capacities. Torque output of the engine511 and the generator 532 are calculated based on detected operationalspeeds of the engine 511 and the generator 532, respectively. Speederror may be calculated utilizing one or two sensors.

In a supplemental embodiment of this general control concept, a commandis issued to increase the torque output of the generator 532responsively to detection of an engine 511 over power condition. A checkfor the continuation of the engine overpower condition is repeated. Thenagain, a continuing overpower condition may be detected in which thetorque output of the engine 511 continues to surpass the torque outputof the generator 532 and a supplemental command is issued to againincrease the torque output of the generator 532. Again, the check for acontinuation of the engine overpower condition is repeated. Ultimately,the engine torque is reduced back to a torque output that is less thanthe torque output of the generator 532 when repeated checks, of apredetermined number, each detects an overpower condition in which thetorque output of the engine 511 surpasses the torque output of thegenerator 532.

In yet another embodiment of this same basic concept, the methodincludes detecting an overpower condition in which the torque output ofthe engine 511 is surpassing the maximum torque output of the generator532; the engine 511 is responsively controlled to a maximum torqueoutput set at a value less than the maximum torque output of thegenerator 532.

Referring now with greater specificity to the drawings, FIGS. 11 and 12comparatively illustrate the present method of control which enables theelimination of a thirty percent (30%) “buffer” that has beenconventionally provided between the torque capacities of the engine 511and the generator 532; the necessity of this buffer resulting in the useof generators 532 significantly larger, or engines 511 significantlysmaller than would otherwise be optimal since thirty percent of one oftheir capacities must be sacrificed to maintain the buffer margin forcontrol, just in case it is needed. By otherwise controlling the engine511 so that it can be assured that the capacity of the torque capacityof the generator 532 will not be exceeded, the approximately thirtypercent of lost capacity can be exploited. Graphically this is shown inFIG. 12 where the speed (ω), plotted on the x-axis, is equalized at theright side of the graph where the maximum torque of the generator(T_(gen) _(—) _(max)) is equal to the torque of the engine 511 when theconstant (K) representing the gearing ratio is considered (T_(eng)/K).The increase in useable speed, and in turn useable power (P=T×ω), fromboth the engine 511 and generator 532 is represented by the distancemoved to the right along the x-axis from the buffered position(K×Δω_(eng) _(—) _(max)) to the “virtualized” position (K×Δω_(eng) _(—)_(max) _(—) _(virt)) where the buffer is virtual, and not actual,because of the control strategy exercised.

Referring now to FIGS. 13-15, the VCU 100 calculates an engine referencevalue (ω_(eng) _(—) _(ref)) and the TMU 230 receives that value and,together with a sensed speed of the motor (ω_(motor)), taking intoaccount the gearing ratio consequence, a generator reference speed(ω_(gen) _(—) _(ref)) is calculated and passed forward for comparison,by summation, with the actual generator speed (ω_(gen)). The result ofthat comparison is then processed through a proportional integralcontroller (PI) for, among other things, amplifying the error value and“learning” error patterns that continue over periods of time based onhistorical values. The learning process is enabled by performingrepetitive calculations. From the PI controller, a generator torquereference (T_(gen) _(—) _(ref)) is derived. This reference is passed tothe generator torque controller 236 for operational control purposes;i.e., by adjusting current, by adjusting voltage with is accomplishedusing pulse width modulation using transistors in the inverter (see FIG.6). The same reference (T_(gen) _(—) _(ref)) is further processed bysubtracting therefrom the maximum torque capacity of the generator(T_(gen) _(max)(ω_(gen))). The sense, whether positive or negative, ofthis outcome is then determined; if negative, the maximum torquecapacity of the generator has not been exceeded; if positive, themaximum torque capacity of the generator has been exceeded. If positive,the capacity of the generator is being exceeded. This positive value isthen multiplied by the constant K to take into account the effect of thegearing ratio and thereby calculating a modification torque(T_(modification)).

To the ECM 220, an engine torque reference (T_(eng) _(—) _(ref)) issupplied from the VCM 100. At the ECM 220, the engine torque reference(T_(eng) _(—) _(ref)) is compared to the maximum torque of the engine(T_(eng) _(—) _(max)). The smaller (min) of these two values is furtherprocessed by comparison with the modification torque (T_(modification))which is subtracted therefrom producing a modified engine torquereference (T_(eng) _(—) _(ref) _(—) _(mod)). This reference (T_(eng)_(—) _(ref) _(—) _(mod)) is fed forward to the engine torque controller220 for operational control purposes over the engine 511; i.e., foradjusting, among possible parameters, airflow to, fuel flow to and/orignition at the engine 511. In practice, if the generator 532 has notbeen determined to be in a condition overpowering the engine 511 at theTMU 230, then the engine torque reference (T_(eng) _(—) _(ref)) from theVCU 100 will be processed through to the engine 511. If, however, thereis a torque modification value (T_(modification)) from the TMU 230 thatis not zero, the engine 511 will be controlled to eliminate thecondition in which the engine torque exceeds that of the generator 532.

A primary benefit of the above described arrangement is that a singlecontroller, the TMU 230, provides both the (ω_(eng) _(—) _(ref)) and the(ω_(eng)). This avoids the possibility of introducing errors that areattributable to mis-calibrations that can otherwise occur when multiplecontrollers are employed for similar purposes. Still further, a maximumengine torque limit (T_(eng) _(—) _(max) _(—) _(lim)) may be derived atthe TMU 230 to provide dc over-voltage protection, but which is affectedat the engine torque control unit 220.

In the embodiment illustrated in FIG. 14, two PI controllers areincorporated. In the embodiment of FIG. 15, the modified engine torquereference (T_(eng) _(—) _(ref) _(—) _(mod)) and the maximum enginetorque limit (T_(eng) _(—) _(max) _(—) _(lim)) are rationalized toproduce the maximum engine torque limit (T_(eng) _(—) _(max) _(—)_(lim)) that will be utilized by the engine torque controller 220.

Although the present invention has been described and illustrated indetail, it is to be clearly understood that the same is by way ofillustration and example only, and is not to be taken as a limitation.The spirit and scope of the present invention are to be limited only bythe terms of any claims presented hereafter.

What is claimed and desired to be secured by Letters Patent is asfollows:
 1. Arrangement for a compact battery and cooling systemtherefore, said arrangement comprising: a plurality of elongate batterycells, each battery cell having a longitudinal axis and a hexagonalcross-sectional shape in a plane oriented substantially perpendicular tosaid longitudinal axis; said plurality of elongate battery cells beingparallelly oriented, each to the others, within a battery housing; saidplurality of battery cells being arranged in a honeycomb configurationwith opposed faces of adjacent battery cells proximately located one tothe other in face-to-face relationship; and at least one substantiallyhexagonally shaped cooling channel provided at an interior locationwithin said plurality of battery cells a thermally radiative caparranged in fluid communication with said at least one substantiallyhexagonally shaped cooling channel; and said radiative cap and said atleast one substantially hexagonally shaped cooling channel containingcooling fluid that circulates therebetween for cooling said plurality ofbattery cells.
 2. The arrangement as recited in claim 1 wherein said atleast one substantially hexagonally shaped cooling channel is aplurality of hexagonally shaped cooling channels arranged within saidplurality of battery cells.
 3. The arrangement as recited in claim 1further comprising: an air circulation system having an air inletexposed to an exterior of a carrying vehicle for intaking air having atemperature in a range suitably low for absorbing heat from saidradiative cap; and a circulation path that directs air drawn into saidair circulation system through said air inlet across said radiative capand way therefrom for cooling said battery cells.
 4. The arrangement asrecited in claim 1 further comprising: an air circulation system havingan air inlet exposed to a passenger compartment of a carrying vehiclefor intaking air having a temperature in a range typically suited forpassenger comfort; and a circulation path that directs air drawn intosaid air circulation system through said air inlet across said radiativecap and away therefrom for cooling said battery cells.
 5. Thearrangement as recited in claim 4 further comprising: said aircirculation system having an air exit ported to an exterior of thevehicle.
 6. The arrangement as recited in claim 4 further comprising:said radiative cap having a plurality of fins extending from anexteriorly exposed surface thereof for enhancing thermal discharge ofheat from said radiative cap to air circulated across said fins.
 7. Thearrangement as recited in claim 6 further comprising: said cooling fluidbeing water maintained under vacuum, said vacuum of sufficient magnitudeto establish a boiling point of said water at a temperature below apredetermined level for potentiating the life of said battery.
 8. Thearrangement as recited in claim 7 further comprising: said predeterminedtemperature at which said cooling fluid boils being approximately 40°centigrade.